Control system responsive to two reversible voltages



Em? a April 27. 1954 D. J. SIKORRA 2,677,085

CONTROL SYSTEM RESPONSIVE TO TWO REVERSIBLE VOLTAGES Filed Feb. 9, 1951 2 Sheets-Sheet 1 paw X M15 0 M070? wow/r A D. J. SIKORRA CONTROL SYSTEM RESPONSIVE TO TWO REVERSIBLE VOLTAGES Filed Feb. 9, 1951 2 Sheets-Sheet 2 Patented Apr. 27, 1954 CONTROL SYSTEM RESPONSIVE T TWO REVERSIBLE Daniel J. Sikorra, Allis-Chalmers waukee, Wis.

VOLTAGES Milwaukee, Wis assignor to Manufacturing Company, Mil- Application February 9, 1951, Serial No. 210,134

11 Claims. I

This invention relates in general to improvements in electric control systems and in particular to means for controlling a dynamoelectric machine to limit the magnitude of operating conditions thereof.

Dynamoelectric machine control systems are known in which means which are normally operative to maintain constant a first operating condition of the machine, such as voltage, current, speed or power, are overcome by the action of protective means responsive to a second operating condition of the machine attaining a limiting value. In most of such systems, the electrical signal from the protective means completely overcomes the signal responsive to the first operating condition, so that the first signal has no effect on the control of the motor until the second condition has returned to a desired value. Such systems usually compare voltages or currents proportional to the operating conditions and utilize the difference between the compared quantities to return the second operating condition to a desired value.

Such systems have the disadvantage that if, at the time the second operating condition exceeds the limiting value, the first operating condition is such that the first signal tends to cause the second operating condition to further exceed the limiting value, the magnitude of the second signal must be greater than the magnitude of the first signal to produce any limiting effect and the limiting eiTect will only be proportional to the difference between the two signals, thereb decreasing the corrective signal available. An additional disadvantage of such systems is that they provide no means for utilizing the first signal to aid in preventing the second operating condition from substantially exceeding the limiting value.

'lhe above disadvantage may be overcome by utilizing a control system in which the first signal is effective to aid the second signal in preventing the second operating condition from substantially exceeding the predetermined limiting value.

It is therefore an object of this invention to provide an improved electric control system for the simultaneous control of two operating characteristics of a dynamoelectric machine.

It is an additional object of the present invention to provide a electric control system in which a signal responsive to deviations of a controlled condition is operative to prevent another controlled condition from substantially exceeding a limit value.

" vided with 1. sis-142) Objects and advantages other than those set -forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 diagrammatically illustrates the circuits and apparatus of one embodiment of the invention;

Fig. 2 is a graph including a group of curves illustrating operating characteristics of some of the elements shown in Fig. 1;

Fig. 3 diagrammatically illustrates the circuits and apparatus of an alternate embodiment of the invention; and

Fig. 4 partially illustrates an additional a1- ternate embodiment of the invention.

Referring to Fig. 1, one embodiment of the invention is illustrated controlling operating characteristics of a translating device such as a dynamoelectric machine 6 having an armature 6a and a field winding 6b. Machine 6 may be a direct current motor driving any suitable load device, now shown, and supplied with current from any suitable controllable source such as the armature 8a of a generator 8. Generator 8 is pro a field winding 8b connected across armature 8a in series with an adjustable resistor I ii and the armature Ha of a buck-boost exciter H. Exciter l I is provided with a pair of differentially acting field windings Hc, lid for controlling the voltage of armature I la.

Field windings Hc, lid are energized through a polarized magnetic amplifier l2 in response to variations in the operating characteristics of motor 5. Amplifier I2 comprises a first saturable reactor it provided with a pair of saturable cores !3a, a reactance winding [3b divided into two portions severally wound on the two cores and a control winding I likewise divided into two portions. Amplifier [2 further comprises a second saturable reactor I 4 having a pair of saturable cores Ma, a reactance winding lb and a control winding Mc. Reactance winding I3?) is energized from a suitable alternating current source such as a secondary winding I 5b of a transformer l5 having its primary winding l5a connected to an alternator l6. Reactance winding Mb is likewise energized from alternator I 6 through a secondary winding I of transformer is. Windings I30, Mo comprise control winding means for varying the saturations of cores 13a, Ma.

A first full wave rectifier l8 has its alternating current terminals connected in circuit with windings lt'b, b, and a second full wave rectilii is similarly connected in circuit with windings Mb, 150. A direct current terminal of rectifier It is connected to a direct current terminal of like polarity of rectifier l9 through a common terminal M of field windings lic, Hot. The other direct current terminals or rectifiers is are connected to the other terminals of windings lic, lid, respectively, so that windings ilc, lid are energized in dependence upon the reactances or windings I31), Mb, respectively.

Control windings I30, Mc have impressed thereon a unidirectional signal voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations in the regulated operating characteristic from a desired value. If it is desired to regulate the speed of motor [5, the motor may be provided with any suitable known means, such as a tachometer generator 23, to provide a voltage proportional to the speed of the motor. The voltage of generator 23 is compared with the voltage of a suitable reference source, such as a battery 2d supplying a voltage divider 25 through a reversing switch 26, to produce the desired signal voltage. This signal voltage is impressed between a pair of terminals 2t, 3?! in circuit with resistance means comprising an adjustable resistor 2'! connected across windings ific, idc. Switch 26 is provided with blades 26a and sets of contacts 2%, Etc to reverse the connection of divider 25 to generator 23 to reverse the direction or rotation of motor 6.

To prevent an operating condition or motor t other than the condition being regulated from substantially exceeding a limit value, amplifier i2 is provided with a bias voltage dependent upon the operating condition. if it desired to prevent the current in motor 6 from substantially exceeding a predetermined maximum value, suitable means responsive to'this current are provided, such area third saturabie reactor 3% having a pair of saturable cores 3 l a, a reactance winding 31?) and a saturating winding Sic. saturating winding Sic is connected between generator 2! and motor to be traversed by a current proportional to the current flowing in armature be so that the reactance of winding 35b varies in response to variations in current of motor fi.

Reactance winding Me is connected in circuit with an adjustable resistor 33 and the primary winding 32a of a saturable transformer 32, and these elements are energized from the secondary winding i-i ia of a transformer having a primary winding Edi? connected to machine Resister and winding tlb are bypassed by a resistor Transformer 5:52 is provided with a secondary winding 3% connected to the alterhating current terminals of a full wave rectifier 3t, and a similar full wave rectifier is-connected across resistor 33. Resistors 33, are connected across the direct current terminals of rectifiers 365, El, respectively. One direct current terminal of rectifier i is connected to a direct current terminal oi like polarity of rectifier 3?, so that a voltage proportional to the diiierence between the voltages of winding 32b and of resistor 33 appears between the noncommcn terminals of resistors 38, One cf such noncommon terminals is connected to an adjustable tap 27d of resistor 2'5 and the other noncommon terminal is connected to a common terminal M of windings its, l ic. If required, the regulating system may be provided with any suitable known damping means for stability.

In operation of the system, assuming that switch 26 is in a position to close contacts 26c and that generator 8 is running and has a predetermined polarity, motor 6 runs at a speed and in a direction determined by the voltage and polar-- ity of armature 8a and the fixed current in field winding 6b. Assuming that motor 5 is operating at the desired speed, the voltage of tachometer generator 23 is equal in magnitude and opposite in polarity to the voltage of the adjustable portion of voltage divider so that no signal voltage is impressed on resistor 21 and windings its, l ic by generator 23 and divider 25. Under these conditions, the saturations of cores its, bid are determined by the bias voltage impressed on windings Etc, Me from resistor 33 and transformer 32.

Curve Q5 of Fig. 2 is the volt-ampere characteristic of transformer 32, showing the relation between the voltage of winding and the current in winding 32a. The volt-ampere char" acteristic oi resistor 33 is shown by the straight line it of Fig. The difference between the voltages of resistor .33 and of winding 3223, which difference is proportional to the bias voltage i11ipressed between terminal 4i and adjustable tap Zia, is represented by curve ll of Fig. 2. The axis of abscissa of Fig. 2 is sealed in terms of the c .I'IClll; flowing in the motor armature since reactor 3i acts similarly to a current transformer to supply to resistor 33 and winding a cur rent proportional to the current in armature iia. Fig. 2 shows that for a predetermined current 0A in motor E2, the voltage of resistor 33 is equal to the voltage of winding 3221, so that the bias voltage impressed betwcen terminal ii and tap "lid is zero, and that the polarity and magnitude of this bias voltage vary in dependence upon the di rection and magnitude of variations in the motor current from the value 0A. For motor currents below this value, tap 21a is at a positive potential with respect to terminal 41. Resistor 33 is adjusted so that the current on represents the predetermined limit current which is to be permitted in motor 6.

Ir" resistor was not connected in circuit with windings 32a, the bias voltage would be substantially zero when the motor current is zero, since the reactance of winding 3 lb approaches infinit under this condition and substantially no current would be supplied to resistor 33 and winding 32a. Actually, resistor 35 supplies a small predetermined current to winding 32a from winding 3 in so that at low motor currents the bias voltage fellows line 50 instead of curve ti to provide an initial bias voltage 013 at zero current in motor 6.

With no voltage impressed between terminals 29, lit by tachometer generator and divider and with the motor current below the predeter mined maximum value 0A, the bias voltage inipressed on windings I30, I has a magnitude intermediate zero and OB, depending upon the magnitude of the current in motor 6. Assuming that tap 21a is at the midpoint of resistor 2i, this bias voltage saturates cores ltd, I la equally, producing equal reactances in windings lib, use causing equal currents to flow through diiierentially acting field windings lie, iid. The net magnetomotive force of windings l to, 6 id is zero under these conditions, so that the voltage of armature lid is zero. Assuming that resistor it is adjusted .so that armature 8c supplies to field winding 873 all the current required to maintain the voltage of armature Be at any given value, field winding 8?) maintains the voltage of armature Be at the value required to keep the speed of motor 6 at the desired value.

If the speed of motor 6 increases slightly above the desired value, the voltage of tachometer generator 23 exceeds the voltage of divider 25, producing a signal voltage which causes terminal 30, for example, to become positive with respect to terminal 29. If the motor current is below the maximum value 0A, this signal voltage acts cumulatively with the bias voltage with respect to winding I40, thereby increasing the satura tion of cores Ida and increasing the currents through reactance winding Mb and field winding lid. The signal voltage acts differentially with the bias voltage with respect to winding lite, thereby decreasing the saturation of cores I312 and the currents through reactance winding I31) and field winding I la. An increase in current in field winding lid with respect to the current in field winding lIc produces in armature Ha a voltage which opposes the voltage of armature to, thereby reducing the current through field winding 3b to reduce the voltage of armature 8a to return the speed of motor 6 to the desired value.

If the speed of motor 6 decreases slightly below the desired value, with the current of armature to below the limit value, the action of the regulatin means to return the speed to the desired value is the reverse of that described above.

During acceleration of machine '5 or when the speed of the motor decreases considerably below desired value, the voltage of voltage divider exceeds the voltage of tachometer generator 23 to impress a signal voltage between terminals 29, 332 which, if the motor current is below the maximum value 0A, increases the current through field winding I Ic above the current in winding 1 id to produce in armature Ha a voltage tending to increase the voltage of armature 8a and increase the speed of motor ii to the desired value. Owing to the high gain in machine ll and amplifier l2 the motor current may tend to exceed the predetermined maximum value 0A, during such acceieration. As the motor current approaches the value 0A, the bias voltage is reduced along curve d! to reduce the current through field winding iio until at the current 0A, the bias voltage is zero.

With zero bias Voltage, the signal voltage is ineffective to increase the excitation of winding 81) because the signal voltage saturates cores Eta,

Eda equally to produce equal currents through field windings I I0, I Id, resulting in zero voltage on armature Ila regardless of the magnitude of the signal voltage, to prevent the motor current from substantially exceeding the limit value.

If the motor current increases above the limit value 0A, the bias voltage reverses polarity and increases in magnitude. The bias voltage then acts cumulatively with the signal voltage on winding I and acts differentially with the signal voltage on winding I3c. This action increases the saturation of cores Ma above the saturation of cores [to and increases the current in winding d above the current in winding l 50 to produce in armature Ha a voltage opposing the voltage of armature 8a to reduce the current in field winding 87). This action continues until the current supplied to motor 6 has decreased to the value OA.

lhus, the bias voltage exercises a supervisory control over the signal voltage to prevent the motor current from substantially exceeding the limit value, and if the current does exceed the with respect to terminal 29.

limit value, the action of the bias voltage is to invert the action of the signal voltage to cause the signal voltage to aid in returnin the current to the limit value.

When the speed of motor 6 increases considerably above the desired value, or when it is desired to decelerate machine 6 from a given speed, the voltage of voltage divider 25 is reduced below the voltage of tachometer generator 23 to produce a signal voltage which renders terminal 30 positive with respect to terminal 29. ihis signal voltage acts cumulatively with the bias voltage on winding Mo and acts differentially with the bias voltage on winding [30 to increase the current through field winding lid above the current in field winding Ho and thereby produce in armature I la a voltage opposing the voltage of armature 8a This action reduces the energization of winding 8b to reduce the voltage of armature Ba. If motor 8 is driving a high inertia load, the voltage of motor 6 will then exceed the voltage of armature Ba to cause motor 6 to act as a generator supplying current to drive generator 8 as a motor. This action reverses the direction of current flow between machines 6, 8 and through saturatin winding 3Ic, but does not reverse the polarity of the bias voltage as long as the motor current does not exceed the limit'value because reactor SI is not responsive to the polarity of the current in winding 3 lo.

Motor ii is thus regeneratively braked to the speed determined by the setting of divider 25. If during such regenerative braking the motor current approaches the limit value, the bias voltage is gradually reduced along curve 41 to reduce the energization of field winding Hd to increase the net voltage acting on winding 3b. An increase in the energization of winding 8b increases the voltage of armature 8a to reduce the voltage differential between armatures 6a, 8a and thereby reduce the current flowing between the two armatures. If the current reaches the value 0A the bias voltage is zero to produce zero net magnetomotive force in windings I I0, I Id and zero voltage on armature i la.

If the current in armature to increases above the limit value, the bias voltage reverses polarity and increases in magnitude. This action inverts the action of the signal voltage to cause amplifier I2 to supply current to field winding He in excess oi the current supplied to winding lid to produce in armature I la a voltage aiding the voltage of armature 8a to thereby further increase the voltage of armature ila until the current in armature 511 has returned to the predetermined limit value. Thus, the regulator of this invention operates at, all times to prevent the current in motor 6 from substantially exceeding a predetermined value independently of the polarity of the motor current.

To cause motor 6 to rotate in the direction opposite to that described above, switch 26a is moved to close contacts 26?) to impress across resistor 2? a signal voltage rendering terminal 39 positive This causes the bias voltage and the signal voltage to act cumulatively on winding Hi0 and to act differentially on windin 30 to increase the energization of Winding Ild above the energization of Winding lie. The voltage of armature Ha thereupon builds up to produce across armature 8a a voltage of a polarity opposite to that described above for the forward direction of rotation of motor 6 to cause reverse rotation of motor 6. The system then operates as described above to maintain the speed of motor 6 substantially constant and to prevent the current in motor '6 from substantially exceeding the predetermined limit value.

Fig. 3 illustrates an alternate embodiment of the invention in which reactors I3, I4 are provided with control winding means in the form of signal windings I3d, Md and bias windings ISe, Me. Signal windings I3d, Md are connected to be energized through a pair of conductors tab by a signal voltage equal to the difference between the voltage of tachometer generator 3 and the voltage of the adjustable portion of voltage divider 25. Bias windings I Be, Me are energized through a pair of conductors 480:, @919 by means including a shunt 5| connected in circuit with generator 3 and motor 6. The alternating current terminals of a full wave rectifier 52 are connected to shunt 5| and the direct current terminals of rectifier 52 are connected across a voltage divider 53 to impress across divider 53 a volt' age of a fixed polarity proportional to the current of either polarity in motor t. Bias windings I 36, I 46 are serially connected with each other across divider 53 in series with a battery which opposes the voltage of divider 53.

Windings I3d, I3e, led, I l-e are so connected that one of the bias windings Its, Me acts differentially with respect to its associated signal winding and the other bias winding acts cumulatively with respect to its associated signal winding for one direction of current flow through the windings, and the one bias winding acts cumu-- latively with its associated signal winding and the other bias winding acts differentially with its associated signal winding for the other direction of current flow through the windings.

In operation, assuming that motor is operating at the desired speed, the voltage of tachom eter generator 23 is equal to the voltage of divider 25 so that no voltage is impressed across signal windings Iild, Md. If the current in motor E3 is below the predetermined limit value, the veltage of battery 54 exceeds the voltage of divider 53 by an amount determined by the magnitude of the motor current to impress across bias windings I3e, I 4e a predetermined bias voltage. With no voltage across signal windings I 3d, i l-d, this bias voltage saturates cores I3a, Ida equally to cause equal currents to flow through field wine.- ings IIc, Ild. These equal currents in windings II 0, Hal cause the voltage of armature II a to be zero so that machine 3 maintains the speed of motor 6 at the desired value.

If the speed of motor 6 increases slightly above the desired value, the voltage of generator 23 increases above the voltage of divider 25 to impress a signal voltage across signal windings Itd, Md. This causes windings Md, Me to act cumulatively to increase the saturation of cores Ida and causes windings ISd, [3.2 to act difiierentialiy with respect to each other to reduce the saturation of cores I3a. This action increases the current through field winding I I d with respect to the current through field winding I I c to produce across armature Ila a voltage opposing the volt age of armature 8a, thereby reducing the energization of field winding 31) and returning the speed of motor 5 to the desired value.

If the speed of motor 6 decreases slightly below the desired value, the voltage of divider 25 exceeds the voltage of generator 23 to produce signal voltage which increases the current through field winding IIc with respect to the current in field winding lId to return the motor speed to the desired value.

If, during acceleration of motor 6 or when the speed of motor 6 decreases considerably below the desired value, with the energization of field winding IIc exceeding the energization of field winding I Id to bring the motor up to the desired speed, the current in motor 6 increases toward the limit value, the voltage of divider 53 approaches in magnitude the voltage of battery 54 to reduce the bias voltage impressed on bias windings I3e, Ite, thereby reducing the energization of winding I I0. When the motor current reaches the predetermined limit value the voltage of divider 53 equals the voltage of battery 54 so that no voltage is impressed on bias windings i3e, I 4e.

The signal voltage then produces equal saturations in cores I3a, I la so that the currents through windings IIc, IId are equal to produce a net magnetomotive force of zero in these windings.

If the motor current increases beyond the limit value, the voltage of divider 53 exceeds the voltage of battery 54 to reverse the polarity of the voltage applied to bias winding I 3e, I ie. This inverts the action of the signal voltage, in Fig. 1, to cause the energization of field wind ing I Id to exceed the energization of winding I is to return the motor current to the predetermined limit value.

Thus, the embodiment of Fig. 3 operates in a manner similar to that described above in connection with Fig. 1 to maintain the speed of motor 5 substantially constant and to prevent the motor current from substantially exceeding a predetermined value.

4 illustrates an additional alternate em bodiment of the invention in which the bias volt" age, obtained from a suitable source, such as voltage divider 5-3 and battery 54 as in Fig. 3, is impressed across resistor 27 which is connected to the control windings I30, Me as in 1. The signal voltage, obtained from a suitable source such as tachometer generator 23 and voltage divider is impressed between the adjustable tap 2hr of resistor 2! and the common terminal ii of windings I to, I40. Thus, the connections of the bias and signal voltage sources in i are the reverse of the connections illustrated in Fig. 1. However, the embodiment of Fig. t operates in a manner identical to that described above in connection with Fig. 1 to maintain the speed of motor is substantially constant and to prevent the motor current from substantially ex ceeding a predetermined value.

Although but a few embodiments of the pres ent invention have been illustrated and described. it will be apparent to those skilled in the art that various changes and modifications may be therein without departing from the spirit of the invention or the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source of current for supplying said motor, a polarized magnetic amplifier comprising a first saturable reactor having a first reactance winding and a first control winding and a second saturable reactor having a second reactance winding and a second control winding, means including a tachometer generator responsive to the speed of said motor for producing a signal voltage having a magnitude and a polarity dependent upon the magnitude and direction of variations in the speed of said motor from said predetermined value,

means connected to said motor for producing an alternating voltage substantially proportional to the magnitude of the current flowing in said motor, means energized by said alternating voltage for producing a bias voltage having a magnitude and a polarity dependent upon the magnitude and direction of variations in said current from a predetermined limit value, means for impressing said bias voltage and said signal voltage on said control windings, whereby the saturations produced in the difierent said reactors by said signal voltage are varied oppositely by said bias voltage and the saturations of said reactors are equal when said bias voltage has zero magnitude, and regulating means connected to said reactance windings to be energized in dependence upon the difierence between the saturations of said reactors for controlling the supply of current from said source to said motor to maintain said speed at said predetermined value and to prevent said current from substantially exceeding said limit value.

2. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a polarized ma netic amplifier comprising a first saturable reactor having a first reactance Winding and a first control winding and a second saturable reactor having a second reactance winding and a second control winding, means including a tachometer generator responsive to the speed of said motor for producing a signal voltage having a polarity and magnitude dependent upon th direction and magnitude of variations in said speed from said predetermined value, a common terminal for said first and second control windings, a resistor connected between the other terminals of said first and second control windings, means for impressin said signal voltage across said resistor, means connected to said motor for produoing a bias voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said motor current from a predetermined limit value, an adjustable tap for said resistor, means for impressing said bias voltage between said common terminal and said adjustable tap, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage and the saturations of said reactors are equal when said bias voltage has zero magnitude, and regulating means connected to said reactance windings to be energized in dependence upon the difference between the saturations of said reactors for controlling the current supplied from said source to said motor to maintain the speed of said motor substantially constant at said predetermined value and to prevent said current from substantially exceeding said limit value.

3. In a system for maintaining the speed of a direct current motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a pair of differentially acting field windings for controlling the flow of current from said source to said motor, a first saturable reactor having a first reactance winding and a first control Winding, a second saturable reactor having a second reactance winding and a second control winding, speed responsive means connected to said motor for producin a signal voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in the speed of said motor from said predetermined value,

means connected to said motor for producing a bias voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said current from a predetermined limit value, means for impressing said bias voltage and said signal voltage on said control winding, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage and the saturations or" said reactors are equal when said bias voltage has zero magnitude, and means connecting said field windings to said reactance windings to ener ize said field windings in dependence upon the diiierence between the saturations of said reactors to maintain the speed of said motor substantially consistent at said predetermined value and to prevent said current from substantially exceeding said maximum value.

4. In a system for maintaining the Speed of a direct current motor substantially constant at a predetermined value, the combination of an electric generator for supplying current to said motor, a first saturable reactor having a first reactance windin and a first control winding, a second saturable reactor having a second reactance winding and a second control winding, speed responsive means connected to said motor for producing a signal voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in the speed of said motor from said predetermined value, a common terminal for said first and second control windings, resistance means connected between the other terminals of said first and second control windings, means for impressing said signal voltage across said resistance means, a third saturable reactor having a saturating winding and an inductive winding, means connecting said saturating winding between said generator and said motor, a source of alternating current, a resistor, a saturable transformer having a primary winding and a secondary Winding, means connecting said inductive winding, said resistor and said primary windin in circuit with each other across said source of alternating current to impress on said resistor and said primary winding a voltage proportional to the magnitude of the current supplied to said motor, means including rectifier means connected to said secondary Winding and to said resistor for producing a bias voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said motor current from a predetermined limit value, an adjustable tap for said resistance means, means for impressing said bias voltage between said common terminal and said adjustable tap, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage and the saturations of said reactors are equal when said bias voltage has zero magnitude, and a pair of differentially acting field windings connected to said reactance windings to be energized in dependence upon the difierence between the saturations of said reactors for controlling said generator to maintain said speed substantially constant at said predetermined value and to prevent said motor current from substantially exceeding said limit value.

5. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a first saturable reactor having a first reactance winding and first control winding means, a second saturable reactor having a second reactance windin and second control winding means, means including a tachometer generator responsive to the speed of said motor for producing a signal voltage hav ing a polarity and magnitude dependent upon the direction and magnitude of variations in the speed of said motor from said predetermined value, means responsive to the magnitude of the current in said motor for producing a bias volt age having a polarity and magnitude dependent upon the direction and magnitude of variations in said current from a predetermined limit value, means for impressing said bias voltage and said signal voltage on said first and second control winding means, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage, and regulating means connected to said reactance windings to be energized in dependence upon the difference between the saturations of said reactors for controlling said source to maintain the speed of said motor at said predetermined value and to prevent said current from substantially exceeding said limit value.

6. In a system for maintaining the speed of an electric motor substantially constant at a pre-- determined value, the combination of a source for supplying current to said motor, a polarized magnetic amplifier comprisin a first saturable reactor having a first reactance winding and a first control winding and a second saturable reactor having a second reactance winding and a second control winding, means including a tachometer generator connected to said motor for producing a signal voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations in the speed of said motor from said predetermined value, means connected to said motor for producing a bias voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations in said current from a predetermined limit value independently of the polarity of said current, means for impressin said bias voltage and said signal voltage on said control windings, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage, and regulating means connected to said reactance winding and energized in dependence upon the difference between the saturations of said reactors for controlling said source to maintain the speed of said motor at said predetermined value and to prevent said current from substantially exceeding said limit value.

'7. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a first saturable reactor having a first reactance winding, a first signal winding and a first bias winding, a second saturable reactor having a second reactance Winding, a second signal winding and a second bias winding, means connected to said motor for producing a signal voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said speed from said predetermined value, means for impressing said signal voltage on said first and second signal windings, means connected to said motor for producing a bias voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said current from a predetermined limit value independently of the pcparity of said current, means for impressin said bias voltage on said first and second bias windings, whereby the saturations produced in the diiierent said reactors by said signal voltage are varied oppositely by said bias voltage, and regulating means connected to said first and second reactance windings and energized in dependence upon the difference between the saturations of said reactors for controlling said source to main tain the speed of said motor at said predetermined value and to prevent said current from substantially exceeding said limit value.

8. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a polarized magnetic amplifier comprising a first saturable reactor having a first reactance winding and a first control winding and a second saturable reactor having a second reactance winding and a second control winding, means including a tachometer generator responsive to the speed of said motor for producing a signal voltage having a polarity and magnitude dependent upon the direction and magnitude of variations in said speed from said predetermined value, a common terminal for said first and second control windings, a resistor connected between the other terminals of said first and second control windings, means for impressing said signal voltage across said resistor, a shunt connected between said motor and said source, a full wave rectifier connected across said shunt to produce a voltage proportional to the current in said motor, a battery connected to said rectifier for producing a bias voltage having a polarity and magnitude de pendent upon the direction and magnitude oi variations in said motor current from a predetermined limit value, an adjustable tap for said resistor, means for impressing said bias voltage between said common terminal and said adjustable tap, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage and the saturations of said reactors are equal when bias voltage has zero magnitude, and regulating means connected to said reactance windings to be energized in dependence upon the diiierence between the saturations of said reactors for controlling the current supplied from source to said motor to maintain the speed of said motor substantially constant at said pre determined value and to prevent said current from substantially exceeding said limit value.

9. In a system for maintaining the speed of an electric motor substantially constant at a predetermined value, the combination of a source for supplying current to said motor, a first saturable reactor having a first reactance winding, a first signal winding and a first bias winding, a second. saturable reactor having a second reactance winding, a second signal winding and second bias winding, means connected to said motor for producing a signal voltage having a polarity and magnitude dependent upon the di rection and magnitude of variations in speed from said predetermined value, means for im" pressing said signal voltage on said and second signal windings, means connected to said motor for producing a bias voltage having a pol rity and magnitude dependent upon the direction and magnitude of variations in said current from a predetermined limit value, means for impressing said bias voltage on said first and second bias windings, whereby the saturations produced in the different said reactors by said signal voltage are varied oppositely by said bias voltage, and regulating means connected to said first and second reactance windings and energized in dependence upon the difference between the saturations of said reactors for controlling said source to maintain the speed of said motor at said predetermined value and to prevent said current from substantially exceeding said critical value.

10. In a system for controlling first and second operating conditions of an electric translating device, the combination of regulating means for controlling said conditions, a polarized magnetic amplifier comprising a first saturable reactor having a first reactance winding and first control winding means and a second saturable reactor having a second reactance winding and second control winding means, means connecting said reactance winding; with said regulating means to cause said regulating means to be energized in dependence upon the difierence between the saturations of said reactors, means connected to said device for producing a signal voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations of said first condition from a predetermined value, means for producing a reference voltage, means connected to said device for producing a control voltage proportional to said second condition, means responsive to the difference of said reference voltage and said control voltage for producing a bias voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations in said second condition I.

from a predetermined limit value, and means for impressing said bias voltage and said signal voltage on said control winding means to cause the saturations produced in the different said reactors by said signal voltage to be varied oppositely by said bias voltage, said regulating means being energized in the direction to increase the magnitudes of said conditions when said bias voltage and said signal voltage act cumulatively on said first control winding and said regulating means being energized in a direction to decrease the magnitude of said conditions when said bias voltage and said signal voltage act cumulatively on said second control winding means, whereby said bias voltage and said signal voltage act cumulatively on said second control winding means when said second operating condition exceeds said limit value to energize said regulating means in a direction to prevent said second condition from substantially exceeding said limit value.

11. In a system for controlling first and second operating conditions of an electric translating device, the combination of regulating means for controlling said conditions, a polarized magnetic amplifier comprising a first saturable reactor having a first reactance winding and first control winding means and a second saturable reactor having a second reactance winding and second control winding means, means connecting said reactance windings with said regulating means to cause said regulating means to be energized in dependence upon the difference between the saturations of said reactors, means connected to said device for producing a first control voltage responsive to the magnitude of said first condition, means for producing a first reference voltage, means responsive to the difference of said first control voltage and said first reference voltage for producing a signal voltage having a polarity and a. magnitude dependent upon the direction and magnitude of varations of said first condition from a predetermined value, means for producing a second reference voltage, means connected to said device for producing a second control voltage proportional to said second condition, means responsive to the difference of said second reference voltage and said second control voltage for producing a bias voltage having a polarity and a magnitude dependent upon the direction and magnitude of variations in said second condition from a predetermined limit value, and means for impressing said bias voltage and said signal voltage on said control winding means to cause the saturations produced in the different said reactors by said signal voltage to be varied oppositely by said bias voltage, said regulating means being energized in the direction to increase the magnitudes of said conditions when said bias voltage and said signal voltage act cumulatively on said first control winding and said regulating means being energized in a direction to decrease the magnitude of said conditions when said bias voltage and said signal voltage act cumulatively on said second control winding means, whereby said bias voltage and said signal voltage act cumulatively on said second control winding means when said second operating condition exceeds said limit value to energize said regulating means in a direction to prevent said second condition from substantially exceeding said limit value.

References Cited in the file of this patent UNITED STATES PATENTS 

